TBM jamming mechanism and control measures in deep buried tunnels

TBM is widely used in China at present. However, when it is driven in deep buried weak rock tunnels, shield is probably jammed and serious consequences may occur, so it is necessary to study shield jamming mechanism and control measures. Firstly, according to the research results of rheological deformation of the surrounding rock of circular tunnels based on the Hoek-Brown criterion and taking segment lining and tunnel face effects into account, a model for calculating the deformation of the surrounding rock in shield area is established. Secondly, the relevant models for judging jamming state during downtime and continuous excavating conditions are proposed based on the above deformation model and coordinating conditions between the surrounding rock and the shield. Moreover, the rheological effects are taken into consideration in two judged models. Thirdly, control measures for jamming are studied based on the research results of jamming mechanism. The formulae for calculating the critical over-excavation amount are deduced; meanwhile, the models for calculating the critical forepoling strength are also deduced when the over-excavation and forepoling measures are used together. Finally, the above proposed models are applied in an engineering example.